Superheater with boiler



April 2, 1935. 5 COOPER 1,996,099

SUPERHEATER WITH BOILER Filed Feb. 18, 1935 O O O O Q 0 O O O O O 9 O O O O O O O O O 0 00000000 0000000 0000000 00000000 0000000 0000000 000000 ooooooooo ooooo o ooooooooo 00000 0000000000 /3 r A I l N 7 w" F TOR I er ATTORNEY Ji BYQ/M for its purpose the provision of anarrangement Patented Apr. 2, 1935 I I SUPERHEATERWITH BOILEii Roland S..Co0per', River Forest, 1111. 'assigno'r to The Superheater CompariysNew York,.N. Y.

Application February is, 1933, seiiarnaeszsse Y j 1 G'Clainis. (c1. 122-47sy This invention relates to superheater boilers in which the superheater receivessubstantially all of its'heat by convection from gases which have given up heat to water-cooled surfaces. It has in which the degree of superheat obtaine'd'shall be more constant than heretofore, withvariations in the load on the boiler.- I

In order to make clear the invention and how it may be put into use, I shall describe it in can;

nection with the drawing filed herewith which shows one illustrative applicationof the invenv that the distribution'of the superheater surface in the-,spa'ce, between the two banks of boiler tubes is' different. This surface is so arranged tion. In this drawing'Figs. 1 and 2;are diagram-- matic boiler-superheater arrangements given for the-purpose of discussing the theoryofthe invention, and Fig. '3 is a longitudinal section through a portion of a boilerf'embody'ing thein vention.

:Referring first to Fig. 1, there is shown herein cross-section and rather diagrammaticallyv a pair of spaced'banks of water tubes I and 2.; Between them is located a superheater 3. The gases for generating steam in the boiler and" for super: heating this steam are provided by a furnace 4 under the lowerbank of watertubes. 'It will be noted that in .such an arrangement the gases give up some ofztheir heat to the lower bank, thereby heating the watersin the tubes of this bank and generating steam,zbefore they strike:

the superheater "tubes; 'Both theoretical considerations and experience show that as the load onsuch a boiler goes up the superheat rises. One

reason for this is that, at greater'loads the gases striking the superheater are hotter than at lower A further reason, which has not been understood heretofore, is as follows. It usually happens that at the lower loads the gas velocity acrosssome portions of the superheater, is rela-i tively low and only small amounts of gases flow in contact with such' portions. As the load rises,

the velocity through these portions of the superheater becomes more nearly a or even entirely equal to that of thegases across the otherpo-rtions so that allof the portions are then worked more completely. This conditioniis' illustrated in Fig. 1 vwhere the offtake 5 for the gases-is shown as being at one side of the housing. With this disposition, the gases in the right-hand part of the pass have a higher velocityat low loads than those in'the left-hand part. The two parts may lie tothe right and left of some line such as 6.v To the left of this line thegas'es are relatively, stagnant and the superheater elements lying in this zone pick up less heat per unit area in a given time than those in the area to the be substantially equally effective. "Thus' the the remedy suggested by me effective. Thisjremedy is brought out diagrammatically in Fig.2. Here the general arrangement of boilflue is just as it was in Fig. 1, but it will be noted that the gases passing throughthose portio-ns of 'superheat will risewith the'load. Just how much: ofjthe risein superheat with'a rise in the load isidueto one of the two causes referred to above 10'. "er tubes, superheater tubes, furnace and offtake l the superheater nearestthe right hand wallcomefin-contact with more superheater surface than,

do those gases which pass; through thespace at points removed from the right-hand wall. The

arrangement shows a 1 gradually decreasing -amount of superheater surface toward the left.,

The effect of this will'be evident; ,As the boiler load rises, instead of as much additional superheating surfacehaving' its eifectiveness increased as was the case in Fig. l andl'as is the casewith' installations as hitherto made, a' progressively decreasing amount is made more effective with such load increase. The increment, in superheat with rising loads is therefore not at the'same rate as with the former arrangements butis at a decreasing rate. {By properly grading the decrease in the amount of superheating-surface the tend! It will be. understood. of course that the dia The gas currents of the higher velocity at the lower" grammatic: showing is merely illustrative.

loadings of the boiler are in the case shown in the'two figures, confined to the right portion of 3 the spaceand this area expands toward the left with an increase in load. This is due to the fact that the outlet for, the gases is at the right. ,;In

general the engineer practicing my invention will determine in the first'placethrough which pur tion of the space the higher velocity currents travel at low loads and through which spaces the velocity of. the gases atthe low loads is smaller; He'will then be in a position to design his super heater so that there is more superheating surface to be touched by the gases passing throug-hthe former portionsof the space and decreasinglyless in those spaces which progressively experience an increase in their relativevelocity;

Fig, '3 will illustratethis' in a practical instal- 7' lation. .A so-called interdeck "superheater' arrangement is here shown in a horizontal'water tube boiler. The lower bank'of boiler tubes lo the upper bank 2a connect the headers 9 and l0; Nipples ll|l and I2 andfcirculators' l3 connect the headers'to each other and tothe -drum LL Steam is taken ofi'frornthe drum H by the steam pipe l5 and carried "to the superheater inlet header Hi from which it flows through r the superheater to the outlet header 11.: Th's'u-Y "perheater elements l8 are placed between thejtwo t 'ples'and the baffle I 9. V This is a-common andwell banks of tubes in the space between one set of nip known arrangement. In the past the superheat' er surface was uniformlydistributed between-the bafile l9 and the nipples l I. In accordance with my invention,- however; the superheater surface to be passed over by thehotgases decreasespregressively from the baffle toward theinipples' because it is my'observation that at lowloads the f gases-flowing through a space between the b anie I9 and some such line as indicated atiahave' a grcatr'velocity-thanthose flowing through the remaining part of thepassand'that with an inthe degree o'fsuperheat obtained'may @hand corner ofthe setting and then following the roof toward theleft to passdownwardthrough.

crease in the load on the-boiler the velocity of the gases equalizes' more and more through th ev space to the right of the line 6a. Itwill' be seen that by properly proportioning these relative amounts and the rate of decrease of the-surface,

constant for varying loadsl .7

in Fig.3 the velocities ofgas flow at low loads in a particular installation, may for some reasons not be as assumed, out thej greater velo'citiesmay occ'urin some other region, as for example adjar cent tovtheright handnipplesv ll rather than 'to thebailles i9, these-gases reachingthe upper right the secondpa'ss'. It will" beclear that'inthat case. the superheater surface, will havefto be earfrangeddiiierently but that it will beequally posksible'ito practice my'inventionp In any. case, all" that the designing engineer must determine is "just where the high velocities occur'at low loads ,and what-jspaeehas'gases of lower .yelocities at such low loads but has the flow sped up asv the load on the boiler increases. He willthen'be ready toapply. the principles of the inventionto'.

' a the installation in question. 7

der'stood that I am not thereby confining myselff to-this type of boiler. It will-. loe-obvious that the invention has'similar application to other.

YWhatI claim is;

' l; A convection heated v s V ranged relatively to thegasflow over it that: the s a steam and, gas flojw rate considerably below I havechosen arhorizontal water tube. boiler in whichito show-my invention but it" will be'unboilers,

gas stream eifective in heating superheater surface increases in width as the steam flow through the superhcat increases and that beginning at the intended maximum rate, the amount'of Su- I e perheater 7 surface touched by' the effective gases increases at a'smaller frate'than -the width of' the effective gas stream," whereby the rise" of superheattemperature with increased o'utput'is 7 reduced." -l

a 2. In a convection-heatedsuperheater'; apass .for. hot gases wherein thelvelocity of gas flow in one part of the'cross-seotion of the pass is greater superheater so arg than in other'parts, the proportion of part of the total increasing with the load on thesuperheater, and a superheater arranged in'said pass in sucha way that with'a certain' load much below the maximum-"intended load on the] superheater only a certain amount of thesupe'rheater surface is touched by the'greaterr-velocity gases,

and that this proportion increases with' mmcrease of' theload but at a rate lower than that I of the increase in the proportion of the part of greater Velocity gas flow, whereby the rise' in superheat t ernperature with load is reduced;

3. In'a boiler having a gas pass infwhich the width of -the"feffective gasstream increasesin width with theload on theboiler, a superheater to raise the temperature of, the steamlfr'omuthe boiler arranged in said, pass, theamount of super:

heatersurface touched by the effective gases increasing at a uniform rate for increases L of. loadfrom a minimuxnup to a certain point and then increasing 'ata diminishing'rate, said point being relatively far below maximum load, t

1. i. In apparatus. of the olassgdescribed a con-J vection-heatedf .superheater in 1 a through whichheating gases pass inrs'uch aimanner that at one rate of total gas flow through the pass the velocity in, one portion offthe cross-section ofthepass is greater than atfthe remaining jportions a f and that the portion-ofrelatively greater velocity. It is possible that in boilers of thetype shown increases as the ratej ofgl otal. gas flow increases, the superheater ,surface1 being so distributed 'through the'pass thatfifor equal increases of the portion of, higher relative gas velocity'diminish ing 'incrementsof superheater surface: touched by higher velocity gases "are added; the difference in 'therate at which. theihi'gher velocity gasarea increasesI and the rate'ajtiwhich the superheater :surf ace touched by higher velocitygasesincreases being such that the rate at whichthe finalsteam temperature varies withload variation" is mate rially affected.

f 5.1 In a boiler having a .'gaspass wherein; at low.

boiler loads the velocity of l'gas :flo'w is greater in'onepart oithe-crossesection of the pass than: in the other ;,parts. and wherein with a rise .in the load the greater-gasg-velocitypart of the cross"- section increases, a superheater in said pass with [its surface so distributed that at low'loads'gthe greater-velocity gases 5 touch 7 Ta. certain amount of the surface and'that with an'incre'ase'inload above an amount much below the intended'maxi mum the vamount'of surface' touchedfby'izthe greater-velocity gasesxincreases ibut ate-slower ratethan the partof the cross-section occupied by greater-velocity (gases-increases, whereby the rise in superheat temperature with 'l oad increase is reduced l. r r

l -6. In a boiler, a gas through whichthe gas flow is suchthat'through a portion adjacent 7' to oneside'of thegpass and in'creasing infsize with the total g8 .S 'fiOW the, gas yelocity'is higher than outside'of 'sa'idportiom'and s perneamr whosesurfa'ce-is so distributed through said pass that for a certain distanceinward from "said side it increasesauniformly with the"distance from 

